This application relates generally to rotary machines and more particularly, to a secondary sealing assembly for sealing a rotary machine.
At least some rotary machines, such as steam turbine engines, have multiple defined fluid flow paths extending therethrough. A primary flow path includes, in a serial-flow relationship, a fluid inlet, a turbine, and a fluid outlet. A leakage flow path exists in some known rotary machines upstream of the primary flow path. In at least some known rotary machines, the fluid contains particulate debris and leaks into the leakage flow path, thus decreasing the efficiency of the machine and introducing harmful contaminants into the machine. The fluid must be closely monitored and controlled to eliminate the debris that may deposit on internal components of the rotary machine and cause blockage of at least a portion of the flow paths.
Some rotary machines use a plurality of sealing assemblies in the leakage flow path to facilitate increasing the operating efficiency of the rotary machine. Generally, known rotary machines include a primary seal and a secondary seal in the leakage flow path. The primary seal is coupled between a stationary component and a rotary component to provide sealing between a high-pressure area and a low-pressure area. The secondary seal is positioned within the stationary component and is axially movable to facilitate operation of the primary seal. During operation of the rotary machine, a portion of the debris contained in the leakage flow is deposited near the secondary seal and builds up on the stationary components of the rotary machine. This accumulation of debris prevents the axial movement of the secondary seal, which may lead to failure of the primary seal. Failure of the primary seal may decrease the operating efficiency of the rotary machine.
In some known rotary machines, such as gas turbine engines, maintenance of the leakage sealing assemblies may be relatively straightforward. At least some known leakage sealing assemblies in gas turbines engines may be easily disassembled from the rotating shaft and cleaned of any debris buildup. However, is some known rotary machines, such as steam turbine engines, maintenance of the secondary seal may be challenging. At least some known steam turbine engines may be operated continuously for a period of years, thus facilitating excessive buildup of debris and contaminants on the stationary component near the secondary seal. In addition, at least some known steam turbine engines are extremely large, containing rotatable shafts with diameters larger than 20 inches. Such large internal components add to the complexity of maintenance of the seals of such known steam turbine engines.